The first postnatal year is a period when the rate of psychiatric disorder is high, and a correspondingly high rate of suicide might be expected. Age-adjusted mortality ratios for suicide by women in the first postnatal year were therefore calculated from population data for England and Wales for a twelve-year period. The overall mortality ratio was found to be 17-that is, the actual total was one sixth of that expected. The low rate was not found after stillbirth which was associated with a rate of suicide six times that in all women after childbirth. Women who committed suicide after childbirth most often did so in the first postnatal month and there was a tendency to use violent methods. One explanation of the low rate of suicide is that motherhood exerts a protective effect, and further studies were carried out to explore this possibility. In study two, the age-standardised mortality ratio for suicide during pregnancy was calculated by the same method to be 5-that is, the actual rate was one twentieth of that expected. In study three, the rate of parasuicide by women in the first postnatal year was calculated from catchment area data to be less than half that of age-matched women (odds ratio 0.43). In study four, a cognitive explanation for these results was studied. Women with postnatal depression were found to score less on a questionnaire measuring cognitions related 1 to worthlesness, hopelessness and self-harm than women with depression arising at other times. This result suggests that childbearing women, despite their risk of psychiatric disorder, are protected against suicide and self-harm by their relative absence of suicide-related cognitions, and that such cognitions should be a focus for the treatment of other groups at risk of suicide.